The anniversary of U.K. release of Pink Floyd‘s seminal 1973 album The Dark Side of the Moon happens this month, and in honor of the occasion, the band is hosting an online event this weekend. For just 24 hours beginning at 7:01 p.m. ET this Saturday, the record will stream from beginning to end via the band’s official website. As the album is streaming, fans will have the chance to Tweet messages and photos that will alter a special moon on the website.

Here’s how it works: Fans may tweet their messages using the hashtag #DarkSide40, and the messages will cause a part of the moon up at PinkFloyd.com to darken. On top of that hoopla, a few new takes on artist Storm Thorgerson’s famous prism design on The Dark Side of the Moon's cover will also be revealed each day via the website through this Sunday. In the end, all of the new designs will be united to create a digital poster for fans to download.

Where were you when you first heard Pink Floyd’s Dark Side of the Moon album? Tell us your stories in the comments section below!